DontKnowJack
Full Access Member
Upgraded intake and exhaust. No help. What do I try next?
2500 RPM @ 55 MPH Help!
- Thread starter DontKnowJack
- Start date
dakotajeep
Patrolling
How tall are your tires? It almost sounds like you have 4.10 gears?
Thad
Thad
DontKnowJack
Full Access Member
235/85R16. Door sticker says 3:55. I guess someone could've changed it.
3/4 Ton-O-Fun
90F250 na7.3IDI 4x4
It seems you have an automatic transmission problem. How many shifts does it make from a stop to that speed?
dakotajeep
Patrolling
Same thing with mine. Sticker says 3.55 but I know that the previous owner changed things...
2500rpm is about right with 31 inch tires and a C6 trans. This is why I am looking for a 3.55 rear axle for mine. If I intended to two with it at all I would leave it. Mine was bought with the intent of making it a daily raunner on WMO during the warmer months.
Thad
2500rpm is about right with 31 inch tires and a C6 trans. This is why I am looking for a 3.55 rear axle for mine. If I intended to two with it at all I would leave it. Mine was bought with the intent of making it a daily raunner on WMO during the warmer months.
Thad
david85
Full Access Member
With those tires an 4.10 gears, you should get up to 70-75. Thats about what my truck was good for with 4.10s and C6 auto. 3.55s will get you closer to 85.
2500 @ 55 does sound about right for 4.10s in 3rd (direct ratio) gear though.
I almost wonder if the injector pump governor is keeping the RPMs down.
2500 @ 55 does sound about right for 4.10s in 3rd (direct ratio) gear though.
I almost wonder if the injector pump governor is keeping the RPMs down.
DontKnowJack
Full Access Member
It shifts into 3rd @48 mph.
dakotajeep
Patrolling
I am 100% certain that you have 4.10 gears. Those numbers are identical to mine with 31inch tires, C6 trans and 4.10 gears.
As David pointed out you can definately go faster than 55mph but you will be ******* out the tach! Personally, I keep mine below 60 mph just because I can't stand to rev the crap out of the engine.
Thad
As David pointed out you can definately go faster than 55mph but you will be ******* out the tach! Personally, I keep mine below 60 mph just because I can't stand to rev the crap out of the engine.
Thad
bghnkinf350
Registered User
Are you going to tow with it? If so, you might want to stay with the 4.10s and go with an overdrive set up. Mine was about the same RPM's with a C6 and 4.10s. I changed to 3.55s and a ZF5 and am happy with the revs now (but I have another truck to tow with if I need to.)
DontKnowJack
Full Access Member
Will tow 13000 but not often. Any idea what it would cost to swap my C6 for Z5? Including installation. I can't do it.
bghnkinf350
Registered User
For my total ZF5 swap, it cost me around $800. I did not need any driveshaft work. Get the ZF5 (or reg 5 speed from a Bronco or F150) crossmember and wings to make the install a little easier. I recouped a little of the money by selling the old parts.
bghnkinf350
Registered User
And I would then keep the 4.10s. Make sure that is your actual ratio. If your ratio IS 3.55, then you might have a trans problem.
smolkin
Stuck inside Mobile
I also concur that those are normal numbers for a C-6 with 4.10s. I never had my '84 up past 65, too afraid of having to dodge engine pieces coming through the firewall. That was a big part of my decision to go E4OD. Even though the bulk of my daily driving is around town, the '90 is just nicer to drive because of having that extra gear and lockup. Now, if the mythical C-6 locking converter ever actually happens...that would be the way to go. I'd imagine you'd drop the rpms at cruise by a couple hundred at least.
DontKnowJack
Full Access Member
Im askin the PO if he changed the gears....we'll see.
with my F450's driving with the throttle pinned to the governor is a requirement. why? 4.63 and 5.13 rear gears. these motors than take being hammered. I got 650k out of the one in front of the 4.63 . it was planted in my carrier and hauled 15-17k all day long.
Similar threads
